Pipes and Cisterns Practice Test 2 with solutions

Question : 22 of 40

Marks: +1, -0

Pipe A can fill a tank in 4 hours and Pipe B can fill it in 5 hours. Pipe B is opened 2 hours after Pipe A. Find the time taken by both together to fill the remaining portion of the tank.

2 hours
$2 2/3$ hours
$1 2/{11}$ hours
$1 1/9$ hours
None of these

Validate

Solution:

Part of tank filled by Pipe A alone in 2 hours
=

1/4 × 2

1/2

Remaining portion = 1 -

1/2

1/2

Part of tank filled by A and B in 1 hour =

1/4 + 1/5

9/{20}

Time taken by A and B to fill

9/{20}

part of tank fill
= 1 hour
They taken by A and B to fill

1/2

part of tank =

1 × {20}/9 × 1/2

{10}/9

hours =

1 1/9

hours.

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